A number of organic synthetic reactions using metal complexes as a catalyst have been developed from old and utilized for many purposes. In particular, many reports have been made on asymmetric catalysts that are used in asymmetric syntheses typified by asymmetric isomerization and asymmetric hydrogenation. Among them, metal complexes composed of metallic rhodium and an optically active tertiary phosphine are well known as a catalyst for asymmetric hydrogenation, and a rhodium-phosphine complex using 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as BINAP) as a ligand is reported in J. Am. Chem. Soc., 102, pp. 7932-7934 (1980). Further, it is reported in Inoue et al., Chemistry Letters, pp. 1007-1008 (1985) that asymmetric hydrogenation of geraniol or nerol was performed by using various rhodium-phosphine catalysts to obtain citronellol in an optical yield of 66% ee.
On the other hand, known ruthenium complexes, though there are not so many reports as compared with rhodium complexes, include those having BINAP or 2,2'-bis(di-p-tolylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as T-BINAP) as a ligand, i.e., Ru.sub.2 Cl.sub.4 (BINAP).sub.2 (NEt.sub.3) (wherein Et represents an ethyl group, hereinafter the same) and Ru.sub.2 Cl.sub.4 (T-BINAP).sub.2 (NEt.sub.3), as reported in Ikariya et al, J. Chem. Soc., Chem. Commun., pp. 922 (1985). However, the state-of-the-art ruthenium complexes are not satisfactory in stability as well as optical yield.
Although metallic rhodium provides excellent complex catalysts, it is expensive due to limitations in place and quantity of production. When used as a catalyst component, it forms a large proportion in cost of the catalyst, ultimately resulting in an increase in cost of the final commercial products. While metallic ruthenium is cheaper than rhodium and appears promising as a catalyst component for industrial application, it still has problems in its activity to cope with precision reactions and its range of application.
Therefore, it has been keenly demanded to develop a catalyst which is inexpensive, has high activity and durability, and catalyzes asymmetric reactions to attain high optical yields, i.e., to produce reaction products having high optical purity.